Secondhand Raleigh Junior Rigid MTB: lemon or worth a punt?

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Reynard

Reynard

Guru
Well, we're halfway there! :smile: Took the bar off, and the spacing is now 132.5

So have added another 5 mm, taking the spacing out to 145. Again, will leave that in overnight, and I'm hoping that will be enough. Could hear the metal twanging as I tightened the nuts on the bar.

Extra bonus is that the bent NDS dropout is also now nice and straight. That would explain (in part) why the rear wheel was crabbing when I did my brief test ride.
 
OP
OP
Reynard

Reynard

Guru
Hope this works: I've got to do the same with my son's Dawes Kingpin. It needs spacing from 110mm to 130mm :ohmy:

I'm no expert on bikes, but that is a large deflection, which could potentially lead to problems. I'm not saying it will (one would need to do the relevant maths first to be absolutely sure) but you need to bear in mind:

1) Stress raisers at the brake bridge and at the joins / welds
2) Change in geometry will both alter the way the frame is loaded and the distribution of that loading
3) Potentially significant plastic deflection on fairly thin steel tubing. Pushing this too far will eventually make the metal creep under load, and then *twangggg*

+1 for taking it to a workshop and getting an opinion first, especially since I've seen that this bike is definitely not being used for merely bimbling along. :blush:
 

Gunk

Guru
Location
Oxford
Hope this works: I've got to do the same with my son's Dawes Kingpin. It needs spacing from 110mm to 130mm :ohmy:

I used the same method on my Raleigh Banana to fit a more modern 700c wheeset, it worked fine, but it was only a 10mm stretch.
 
OP
OP
Reynard

Reynard

Guru
I used the same method on my Raleigh Banana to fit a more modern 700c wheeset, it worked fine, but it was only a 10mm stretch.

10 mm on a large bike is doable - it's not just the length of the tubing, but also the angles. Whereas on frame with shorter tubing, by pushing out the axle spacing too far, you'll end up generating forces and moments in places where they weren't designed to be.
 
OP
OP
Reynard

Reynard

Guru
The extra 5 mm I added to the threaded bar yesterday has resulted in another 1 mm of axle spacing, so I'm now at just over 133 mm. I can actually get the wheel in now, but not all the way.

At the moment, the relationship between deflection and permanent deformation is roughly linear (in reality the stress-strain graph in the plastic deformation region is actually slightly curved), so another 10 mm on the bar should do the trick. I will do it in two stages though, just in case.

At least on this bike with this particular geometry, I've needed to add 5 mm of deflection on the bar for every mm gained in axle spacing, so in theory, for an original OLN of 130 mm, I'll have had to wind it out to 155 mm to bring it to an OLN of 135.

Hope this info might be useful for you @DCLane :okay:
 

Gunk

Guru
Location
Oxford
The extra 5 mm I added to the threaded bar yesterday has resulted in another 1 mm of axle spacing, so I'm now at just over 133 mm. I can actually get the wheel in now, but not all the way.

At the moment, the relationship between deflection and permanent deformation is roughly linear (in reality the stress-strain graph in the plastic deformation region is actually slightly curved), so another 10 mm on the bar should do the trick. I will do it in two stages though, just in case.

At least on this bike with this particular geometry, I've needed to add 5 mm of deflection on the bar for every mm gained in axle spacing, so in theory, for an original OLN of 130 mm, I'll have had to wind it out to 155 mm to bring it to an OLN of 135.

Hope this info might be useful for you @DCLane :okay:

Mine took a week of using this method, just a small increment each evening, once I could get the rear wheel in with a slight tug I was happy.
 

DCLane

Found in the Yorkshire hills ...
The extra 5 mm I added to the threaded bar yesterday has resulted in another 1 mm of axle spacing, so I'm now at just over 133 mm. I can actually get the wheel in now, but not all the way.

At the moment, the relationship between deflection and permanent deformation is roughly linear (in reality the stress-strain graph in the plastic deformation region is actually slightly curved), so another 10 mm on the bar should do the trick. I will do it in two stages though, just in case.

At least on this bike with this particular geometry, I've needed to add 5 mm of deflection on the bar for every mm gained in axle spacing, so in theory, for an original OLN of 130 mm, I'll have had to wind it out to 155 mm to bring it to an OLN of 135.

Hope this info might be useful for you @DCLane :okay:

Useful information - and about the bar. I tried getting my mechanical engineering son to help but he's now back at university.

We'll be having a go over the next few weeks. It may work. If it cracks the frame then I've got a problem, particularly as I've just shelled out for a metallic purple paintjob on the Kingpin :ohmy:
 
OP
OP
Reynard

Reynard

Guru
Useful information - and about the bar. I tried getting my mechanical engineering son to help but he's now back at university.

We'll be having a go over the next few weeks. It may work. If it cracks the frame then I've got a problem, particularly as I've just shelled out for a metallic purple paintjob on the Kingpin :ohmy:

Fingers crossed.

Might be a good idea to keep track of progress in graph form; deflection on the x axis and axle spacing on the y. There's nothing quite like a good visual aide memoir in these circumstances.

That way if you see the plot starting to deviate noticeably from what's expected, you'll know it's time to stop before it's pushed too far, and that snazzy new paintjob will live to fight another day. :smile:
 
OP
OP
Reynard

Reynard

Guru
The 5 mm I added onto the bar yesterday was enough to give me the 2 mm I still needed on axle spacing. So in the end, I only needed a displacement of 150 mm to expand the spacing of the dropouts from 130 to 135.

Well, I did say that the relationship between stress and strain is actually slightly curved at this point, so it just shows that this modification is well worth doing in small increments to avoid a potential disaster. I think this is exactly why all the bike websites (e.g. Sheldon) only advocate going up one axle size.

Anyway, the NDS dropout is very nearly straight (likely it will straighten itself over time now anyway as I ride), and the wheel just popped into the dropouts like a dream. One very happy (and relieved) girl here. I think this looks mighty fine, don't you?

NR1F6900_small.jpg


NR1F6901_small.jpg


So I put both wheels on the bike, tipped it the right side up and got the brake pads in a better (but not final) position. Max is starting to look like a real bike again. :hyper: Sorry for the cluttered background, it's been pishing with rain here all day, so I stayed in the garage.

NR1F6902_small.jpg


At this point, I realised that the rear reflector was about as useful as the proverbial chocolate teapot, as it is near enough completely obscured by the rear wheel. That's got nothing to do with the new wheels and tyres - looking back at the original pics of the bike from when I brought it home, it's clear that was always the case. So I removed both reflectors from the bike and put them to one side. I may stick the front one back on, we'll see, but for the rear, I'll probably get some red reflective tape and put a couple of bands of that on each seat stay instead.

What I also did was fit the el-cheapo £5 mudguards from Wilkinsons on that were on the Emmelle. With a bit of jiggery pokery, they went on OK, though how effective they are remains to be seen. My view is that it doesn't cost me to try. If they work well, then the job's a good 'un, but if my feet and derriere get wet and muddy, then's the time to look for something better.

NR1F6903_small.jpg


I'm really chuffed with how this is coming out. Have pretty well much decided to go for everything black e.g. bars, seat post, bottle cage, crankset etc. This will be a really eye-catching bike when it's done.

Next step is to make a decision on the number of sprockets on the rear and do a spot of maths. As mentioned upthread, I'm looking to end up with something similar to the range on the hybrid; it'll give me what I want on the flat, and also have some granny gears in hand if I decide to do an away day somewhere a bit less flat.
 
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